Forming method of tooth trace of gear

Abstract

A forming method of a tooth trace of a gear according to the present invention includes: a first step of preparing a preformed gear made of metal including a cylindrical main body and a tooth part having a flat tooth flank having a uniform thickness in a tooth trace direction inside of the main body; and a second step of conducting a surface treatment locally to an outside surface of the main body in order to deform the outside surface of the main body in such a manner that the same becomes concave, so that a crowning bulging in the tooth trace direction is formed on the tooth flank of the tooth part.

1. A forming method of a tooth trace of a gear, comprising
 a first step of preparing a preformed gear made of metal including a cylindrical main body and a tooth part having a flat tooth flank having a uniform thickness in a tooth trace direction inside the main body, and 
 a second step of conducting a surface treatment locally to an outside surface of the main body under an unrestrained state of the tooth part in order to deform the outside surface of the main body in such a manner that the same becomes concave, so that the tooth part inwardly protrudes at a tooth tip portion thereof, and a crowning bulging in the tooth trace direction is formed on a portion of the tooth flank of the tooth part without the aid of a forming surface. 
 
     
     
       2. A forming method of a tooth trace of a gear according to  claim 1 , wherein
 in the second step, the surface treatment is conducted to a portion of the outside surface of the main body corresponding to a central portion in the tooth trace direction of the tooth part. 
 
     
     
       3. A forming method of a tooth trace of a gear according to  claim 1 , wherein
 the surface treatment is conducted by using a laser beam. 
 
     
     
       4. A forming method of a tooth trace of a gear according to  claim 1 , wherein
 the surface treatment is conducted by using an electron beam. 
 
     
     
       5. A forming method of a tooth trace of a gear according to  claim 1 , wherein
 the surface treatment is conducted by an induction hardening process. 
 
     
     
       6. A forming method of a tooth trace of a gear according to  claim 1 , wherein
 the surface treatment is conducted by a shot peening process. 
 
     
     
       7. A forming method of a tooth trace of a gear, comprising
 a first step of preparing a preformed gear made of metal including a cylindrical main body and a tooth part having a flat tooth flank having a uniform thickness in a tooth trace direction outside the main body, and 
 a second step of conducting a surface treatment locally to an inside surface of the main body under an unrestrained state of the tooth part in order to deform the inside surface of the main body in such a manner that the same becomes concave, so that the tooth part outwardly protrudes at a tooth tip portion thereof, and a crowning bulging in the tooth trace direction is formed on a portion of the tooth flank of the tooth part without the aid of a forming surface. 
 
     
     
       8. A forming method of a tooth trace of a gear according to  claim 7 , wherein
 in the second step, the surface treatment is conducted to a portion of the inside surface of the main body corresponding to a central portion in the tooth trace direction of the tooth part. 
 
     
     
       9. A forming method of a tooth trace of a gear according to  claim 7 , wherein
 the surface treatment is conducted by using a laser beam. 
 
     
     
       10. A forming method of a tooth trace of a gear according to  claim 7 , wherein
 the surface treatment is conducted by using an electron beam. 
 
     
     
       11. A forming method of a tooth trace of a gear according to  claim 7 , wherein
 the surface treatment is conducted by an induction hardening process. 
 
     
     
       12. A forming method of a tooth trace of a gear according to  claim 7 , wherein
 the surface treatment is conducted by a shot peening process.